title: Systematics, biogeography, and character evolution of Sparganium (Typhaceae): diversification of a widespread, aquatic lineage.
abstract: OBJECTIVE
  Sparganium (Typhaceae) is a genus of aquatic monocots containing ±14 species, with flowers aggregated in unisexual, spherical heads, and habit ranging from floating to emergent. Sparganium presents an opportunity to investigate diversification, character evolution, and biogeographical relationships in a widespread temperate genus of aquatic monocots. We present a fossil-calibrated, molecular phylogeny of Sparganium based on analysis of two chloroplast and two nuclear markers. Within this framework, we examine character evolution in both habit and stigma number and infer the ancestral area and biogeographic history of the genus. •
  
  
  METHODS
  Sequence data from two cpDNA and two nDNA markers were analyzed using maximum parsimony, maximum likelihood, and Bayesian inference. We used the program BEAST to simultaneously estimate phylogeny and divergence times, S-DIVA and Lagrange for biogeographical reconstruction, and BayesTraits to examine locule number and habit evolution. •
  
  
  RESULTS
  Two major clades were recovered with strong support: one composed of S. erectum and S. eurycarpum; and the other containing all remaining Sparganium. We realigned the subgenera to conform to these clades. Divergence time analysis suggests a Miocene crown origin but Pliocene diversification. Importantly, the floating-leaved habit has arisen multiple times in the genus, from emergent ancestors-contrary to past hypotheses. •
  
  
  CONCLUSIONS
  Cooling trends during the Tertiary are correlated with the isolation of temperate Eurasian and North American taxa. Vicariance, long-distance dispersal, and habitat specialization are proposed as mechanisms for Sparganium diversification.
authors.affiliation: Department of Botany, University of Wisconsin, Madison, Wisconsin 53706 USA.
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Sulman
authors.forename: Bryan T
authors.initials: BT
authors.lastname: Drew
authors.forename: Chloe
authors.initials: C
authors.lastname: Drummond
authors.forename: Eisuke
authors.initials: E
authors.lastname: Hayasaka
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Sytsma
mesh_terms: D059001:Aquatic Organisms / Q000145:classification* / Q000502:physiology; D044822:Biodiversity; D005075:Biological Evolution; D002467:Cell Nucleus / Q000235:genetics; D018742:DNA, Chloroplast / Q000235:genetics; D035264:Flowers / Q000502:physiology; D016013:Likelihood Functions; D010802:Phylogeny; D058974:Phylogeography; D012098:Reproduction; D017422:Sequence Analysis, DNA; D013997:Time Factors; D032401:Typhaceae / Q000145:classification* / Q000502:physiology
chemical_list: D018742:DNA, Chloroplast
keywords: BEAST; Beringia; Pliocene; Poales; Sparganium; Typhaceae; aquatic habit; biogeography; bur-reed; monocot